wow!

[planet10]

yeah, am looking out for really cheap drivers, not many places around here except charity shops, car boot sales, ebay etc....

If you know what to look for (or are just lucky) some awfully usful drivers can be found in some pretty poor to mediocre boxes -- particularily if you are doing an OB.

Too bad the teleporter is broen... i've got over a 100 candidate drivers....

or this one at Radio Spares....

which looks just like the Monacor SP-200MX and is only £12!

I've a series of mods that seem to wor pretty well on the low budget whizzer coned drivers (the 1st gunea pig were a set of blue & yellow drivers i got for <$20 that popped into the box my pioneer B20s were destined for. next gineau pig is a Fostec FE167.

dave

 

[Godzilla]

re driver placement... should the driver in an OB be placed closer to the floor to minimize reflections off the floor? perhaps closer to the floor but angled upwards?

 

[Scottmoose]

That's what the JE Labs (I believe) OB does. Me, I like larger baffles, but if spaced is restricted, this is probably as good a way as any to achieve it.

 

[2litre]

I was wondering about that too.

Like if you have a high Qts driver placed at 30" vs one placed at say 12" off the floor.

I'm thinking that the one at 12" off the floor would display the 'high Q hump' more than the one at 30", yes?

Conversly, a driver of less Q may have its lower octave enhanced by being closer to the floor.

R/

Jim

 

[Rudolf]

re driver placement... should the driver in an OB be placed closer to the floor to minimize reflections off the floor?

It´s very easy to simulate that at no cost with EDGE www.tolvan.com/edge/
Here are some results:
www.dipolplus.de/images/OB 100_85_60_30_bass.gif
Simulation is for a 100x30cm OB on the floor with driver heights 30cm (red), 60cm (pink) and 85 cm (green).

And here how it is done by simulating the OB including a floor mirror image:
www.dipolplus.de/images/Spiegelquelle.gif

Comparing one result with/without mirror image looks like this:
www.dipolplus.de/images/OB 100_30_floor.gif

Red line without mirror image (floor reflection), green line including floor. OB same as above with driver at 85 cm.
Rudolf

 

[Zero One]

Inrank, here is a pic of the modded and non modded 4 inch drivers, the modded one also has a phase plug made from the cut down cap of a glue tube nozzle, the Phase plug works really well making the highs smoother. These drivers sound brilliant in a double bass setup with sub, I have also used them on winged open baffles and the results were very nice.

 

[Zero One]

Inrank just for interest here is a similarly modded 6.5 inch driver, these also sound good, and I will probably use them on an open baffle. These cost just $5.00 OZ (about $3.20) US and including the mods owe me about $7.50 each. No specs but efficiency is pretty high and they reproduce the highs very nicely as well without a super tweeter.

I have other pics if you need more info.

The phase plug is actually the top of a black whiteboard marker, I go through heaps of these as I run a digital training business, so its a freeby.

 

[Kensai]

Has anyone tried just the Pio B20s with 25ohm inline resistor like Nelson Pass suggested? According to his tests, it looks like this would not only improve the bottom end noticeably, but would also extend its top end to remove the need for a supertweeter.

Actually, according to his article, the measurements he shows for the B20 are after taming the top end in the crossover, so possibly a more elegant solution in this case would be to mod the B20s with phase plugs. Sure, it would take alot more power to run this way, but seems like it would make a good match for common A/V receivers running around these days.

Anyway, the resistor would also significantly increase the B20's Qts which should make it an even better candidate for OB use.

I intend to (eventually) try this myself (don't anyone hold their breath), but I was wondering if anyone had tried either or both with the B20 yet.

Kensai